Shares of Palantir (NYSE: PLTR) rocketed 15.1% higher this week through Thursday trading, according to data from S&P Global Market Intelligence.

Palantir shot up Monday on news the stock would be added to the prestigious S&P 500 index. In addition, the company announced a five-year extension with oil and gas giant BP and hosted its fifth AIPCon, showing off the company's AI platform.

A big achievement

The S&P 500 only admits certain companies that meet several criteria, including positive earnings over the past four quarters, a market cap that's greater than $8.2 billion, and a decently liquid stock.

It's a prestigious honor for Palantir, and now means investors in S&P 500 index funds will be forced to purchase its shares. That's potentially good news for shareholders, as the three S&P 500 index funds from State Street, Vanguard, and Blackrock are the largest exchange-traded funds in the world. The bulk of Palantir's gains came on Monday after the news was announced Friday.

Palantir also announced a five-year extension of its current engagement with BP this week. BP had already been a customer since 2014, using Palantir's "digital twin" simulation for its oil and gas operations. Now with Palantir's year-old AIP platform, BP will incorporate large language models (LLMs) into its workflows for better decision-making.

Speaking of AIP, which is Palantir's AI-powered software that harnesses LLMs for tangible business outcomes, Palantir held its fifth AIPCon on Thursday. AIPCon saw over 100 commercial AIP customers attend, with a handful giving presentations as to how these organizations are benefiting from AIP.

Palantir is firing on all cylinders, but priced for it

The S&P 500 inclusion is a testament to Palantir's recent success. However, is the stock a buy now?

Palantir now trades at over 33 times sales and 82 times its estimated earnings for next year. So, while the company is seeing an AI-powered acceleration, there isn't much margin of safety in buying the stock at these prices.